Wear resistant coating for brake disks with unique surface appearance and methods for coating

ABSTRACT

A brake disk including carbon steel, stainless steel or a ceramic composite material and coated with a coating material that is wear and corrosion resistant and when applied properly allows for the coated surface to have a variety of “textured” appearances. For example, the coated surface can be made to look like woven carbon fiber. The aesthetically pleasing, wear and corrosion resistant coating overlays wear surfaces and portions of the brake disk that will be, in many cases, visible when the brake disk is installed on the vehicle. The coating includes a first layer of a metal, such as a pure titanium metal, and a second layer that can include a Nitride, Boride, Carbide or Oxide of the metal used in the first layer. The coating can be applied using a physical vapor deposition source such as a cathodic arc source with a controlled gas atmosphere.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/711,661, filed May 13, 2015, titled “Wear Resistant Coating For BrakeDisks With Unique Surface Appearance and Methods For Coating;” which inturn is a continuation of U.S. patent application Ser. No. 13/336,986,filed Dec. 23, 2011, titled “Wear Resistant Coating For Brake Disks WithUnique Surface Appearance and Methods For Coating;” which in turn is adivisional of U.S. patent application Ser. No. 12/034,590, filed on Feb.20, 2008 and issued as U.S. Pat. No. 8,084,089 on Dec. 27, 2011, whichclaims priority under 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication Ser. No. 60/890,790, filed Feb. 20, 2007. The disclosure ofeach application listed in this paragraph is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention pertains generally to coated brake disks, drums orany mechanical device that uses friction to transfer kinetic energy, andmethods for coating brake disks and drums. More particularly, thepresent invention pertains to brake disks and drums which have varioussurface finishes that when coated with a wear and corrosion resistantcoating exhibit a three dimensional appearance or surface texture. Thepresent invention is particularly, but not exclusively, useful as abrake disk for use on motorcycles, bicycles, automobiles and any othermotor vehicle.

BACKGROUND

There are a number of reasons why it is important for a brake disk (alsosometimes referred to as a brake rotor) to be wear and corrosionresistant while at the same time looking aesthetically pleasing. First,the ability of the brake disk to resist wear leads to a longer servicelife. A longer service life translates into reduced maintenance and theassociated maintenance costs. Additionally, the ability of the brakedisk to resist corrosion adds to the life and the overall appearance ofthe brake disk. Another consideration for brake disks used onmotorcycles (or wherever the brake disk is exposed to general view), isthe appearance of the brake disk.

During braking, hydraulic or mechanical energy is used to press thevehicle's brake pads against the rotating brake disk. The frictionresulting from the moving contact between brake pad and brake disk slowsthe rotation of the brake disc and decreases the speed of the vehicle.This frictional contact generates heat and causes the contact surfaceson the brake pad and brake disk to wear unevenly. Excessive wear cancause the brake disk to become thin and weak. In some cases, thethinning of the brake disk becomes so severe that the brake disk is nolonger able to support the stresses and heat generated during braking.The result is typically a warped brake disk that can cause undesirablebrake chattering.

A final factor that must be considered when designing brake rotors isaesthetics. Modern motorcycles have rather large diameter brake disksthat are plainly visible, especially the front disk. Because of thisvisibility, the color and surface appearance of a brake disk can add toor detract from the overall look of the motorcycle. These considerationscan affect a purchaser's decision when buying a new motorcycle and whenretrofitting a motorcycle with a new brake system.

In light of the above, it is an object of the present invention toprovide cast iron, carbon steel, stainless steel, and light weightceramic composite brake disks that are coated with a material that iswear and corrosion resistant.

SUMMARY

The present invention is directed to coated brake disks, brake drums orany mechanical device that uses friction to transfer kinetic energy, andmethods for coating brake disks in order to exhibit a three dimensionalappearance. For example, the three dimensional appearance or surfacetexture can be the appearance of a woven or a textured structure on thesurface. The term brake disk is used throughout this document torepresent brake disks, brake drums or any mechanical device that usesfriction to transfer kinetic energy, for example, clutch assembly andfly wheels. In one embodiment a brake disk has one or more surfacefinishes or treatments done (generally referred to herein as surfacefinishing) to the parallel working surfaces which are in turn coatedwith a wear and corrosion resistant coating that exhibits a threedimensional surface appearance or surface texture which is aestheticallypleasing. In one embodiment at least a portion of the parallel surfacesof the brake disk substrate is surface finished to impart apredetermined surface irregularity, modification, design or defect thatexhibit a three dimensional appearance or surface texture. In oneembodiment the surface treatment includes a representation of a logo(for example, identifying a manufacturer) or artistic design. Thesurface irregularity or defect can be variations in the height of theparallel surfaces with angular or perpendicular surfaces between thevariations in the height of the parallel surfaces. In addition thesurface irregularity or modification can be formed as peaks, valleys andangular surfaces between the peaks and valleys. When the parallelsurfaces of the disk brake are subsequently coated with a coating, thedisk brake can exhibit a three dimensional appearance and/or texture.The surface finishing can be achieved, for example, by bead blasting,sanding, grinding, acid etching, photo-resist etching, roll forming,embossing, stamping, honing, lapping, polishing, blanching, milling,profiling.

In one embodiment the thickness of the coating material can vary betweenthe peaks, valleys and angular surfaces to create the predeterminedthree dimensional appearance or surface texture. For example, more ofthe coating can be deposited on the peaks than is deposited on theangular surfaces. The coating material or recipe or construction of thecoating can be selected to achieve the desired three dimensionalappearance or surface texture. Further, the coating material can beselected to achieve different optical characteristics when applied tothe parallel surfaces of the brake disk. The brake disk can bedisk-shaped having a central hole (or in some cases multiple-holes) toallow the brake disk to be positioned over a hub. The brake disk isfurther formed with a pair of flat annular surfaces that extend from thecentral hole to the periphery of the brake disk. These flat surfaces areprovided for contact with the brake pads during braking and constitutethe wear surfaces for the brake disk.

In accordance with an embodiment, the brake disk can include a castiron, carbon steel, light weight ceramic metallic composite, stainlesssteel or a light weight ceramic composite material. A portion of thebrake disk, for example the wear or working surface, is first given aspecific surface finish and then coated with a coating material that iswear and corrosion resistant. Further the coating material can bedeposited on portions of the brake disk that will be visible when thebrake disk is installed on the vehicle. In one embodiment, the coatingis deposited on the entire brake disk.

In one embodiment, the combination of various surface finishes with thewear and corrosion resistant coating impart the three dimensionalappearances to the coated brake disk. The three dimensional appearanceor surface texture can be a woven or textured structure. In oneembodiment the three dimensional appearance or surface texture can beaccomplished by surface finishing at least a portion of the parallelsurfaces of a brake disk substrate to impart variations in the height ofthe parallel surfaces to allow the parallel surfaces to trap particlesof a coating material. The surface finish can be introduced to the brakedisk surface by utilizing a variety of methods. These methods can be assimple as blasting the brake disk surface with a continuous stream ofparticles (commonly referred to as bead blasting) which are typicallyharder than the brake disk surface. These particles can be round inshape or very irregular in shape. The various particle shapes willimpart a different surface finish or surface geography to the brakedisk. For example, with the round particles (of various sizes) andappropriate particle energy (air pressure or hydro pressure) a surfacetexture that microscopically resembles low soft rolling hills can beachieved. With the irregular (crystalline) shaped particles a verycoarse surface geometry (very rugged/jagged peaks and valleys) can beimparted to the brake disk surface. Other methods such as a sanded or aground surface finish can be used to give a different appearance whencoated with the wear and corrosion resistant coating. When the sanded orground surface finish is done in a cross-hatched configuration and thencoated with the wear and corrosion resistant coating the coated brakedisk can exhibit a woven appearance or surface texture such as is foundin components made from carbon fiber. In general, there is a multitudeof surface finish techniques that can be utilized to impart a specificsurface texture or geometry into the brake disk. The techniques for thesurface finishing can include but are not limited to: bead blasting,sanding, grinding, acid etching, laser etching, photochemical etching,roll forming, embossing, stamping, honing, lapped, polished, blanched,milled, profiled or other additional machined surfaces and anycombination(s) thereof. The surface finishing step can also includeetching the surfaces of the brake disk substrate. This process can beused to dissolve unwanted materials such as metals or semiconductormaterials.

In some embodiments, the coating includes a first layer of a materialhaving either an amorphous structure (i.e. a non-crystalline structure)and/or a crystalline structure. In a one embodiment, the amorphousand/or crystalline material is a metal such as titanium, chromium,zirconium, hafnium, boron or an alloy thereof. The first layer isapplied directly on the brake disk. The coating further includes asecond layer that overlays and contacts the first layer. The secondlayer can include one or more metal nitrides, metal borides, metalcarbides and metal oxides. The second layer can also include one or morenitrides, borides, carbides or oxides of the metal used in the firstlayer. For example, for a coating having titanium as the first layer,the second layer can be titanium nitride (TiN). Note; the abbreviations(e.g. TiN) are used herein as a shorthand rather than an exact chemicallabel, and do not suggest that the stoichiometry of the indicatedcompound must be exactly as stated in the abbreviation. Though the termlayer is used herein when discussing the application or depositing ofmaterials, the referred to layers can merge or intermingle such that noclear division exists between the layers.

The layers of the coating can be applied using a physical vapordeposition source such as a cathodic arc source with a controlled gasatmosphere. Other operable techniques such as unbalanced magnetronsputtering or thermal evaporation may also be used. During coatingdeposition, the brake disks are positioned on a fixture and the fixtureis rotated in a planetary movement about a central axis. In greaterdetail, the fixture includes three or more parallel poles that aremounted on a plate and arranged wherein each pole is spaced at an equaldistance from the other poles. A plurality of brake disks can be stackedon each pole, with spacers to separate adjacent disks within each stack.The poles are spaced from each other to allow the brake disks on onepole to overlap the brake disks on an adjacent pole. The spacers preventbrake disks on one pole from contacting the brake disks on an adjacentpole.

BRIEF DESCRIPTION OF DRAWINGS

The details of the present invention, both as to its structure andoperation, may be gleaned in part by study of the accompanying drawings,in which like reference numerals refer to like parts, and in which:

FIG. 1 is a perspective view of a motorcycle having a disk brake system;

FIG. 2 is a perspective view of a coated disk brake;

FIG. 3A is an enlarged cross-sectional view of a portion of the coateddisk brake shown in FIG. 2 as seen along line 3-3 in FIG. 2 showing thecoating layers;

FIG. 3B is an enlarged portion of FIG. 3A.

FIG. 4 is a front elevation view of a fixture for supporting the diskbrakes during the coating process;

FIG. 5 is a top plan view of a fixture for supporting the disk brakesduring the coating process;

FIG. 6 is a schematic plan view and control diagram of a depositionapparatus for use in the invention;

FIG. 7 is a schematic perspective view of a detail of the depositionapparatus of FIG. 5 ; and

FIG. 8 is a schematic cross-sectional view of a cathodic arc source,taken along lines 8-8 of FIG. 7 .

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1 , motorcycle 10 is shown that includes a disk brakesystem. As shown, the disk brake system includes a brake disk 12 that isattached to the front wheel 14 of the motorcycle 10 for rotationtherewith. The brake system further includes a caliper 16 having a pairof brake pads that can be selectively applied against the brake disk 12using hydraulic pressure to slow the rotation of the brake disk 12 andwheel 14. In a typical setup, the hydraulic pressure is provided by themotorcycle operator using a hand lever mounted on the handlebars of themotorcycle 10. A similar system can be applied to the rear wheel of themotorcycle 10.

A better appreciation of a brake disk 12 can be obtained with referenceto FIG. 2 . As shown, the brake disk 12 is disk-shaped having a centralhole 18 to allow the brake disk 12 to be positioned over the hub of thewheel 14 (shown in FIG. 1 ). The brake disk 12 is further formed withflat annular surfaces 20 a,b (see also FIG. 4 ) that extend from thecentral hole 18 to the periphery 22 of the brake disk 12. As shown, flatsurface 20 a is parallel with and opposed to flat surface 20 b on thebrake disk 12. These flat surfaces 20 a,b are provided for contact withthe brake pads during braking and constitute the wear surfaces for thebrake disk 12. In addition, it is flat surfaces 20 a,b that receive thesurface finish prior to coating with the wear and corrosion resistantcoating. In one embodiment, the brake disk is surface finished to imparta three dimensional appearances to the brake disk before the brake diskis coated. The three dimensional appearance or surface texture can be awoven or textured structure. In one embodiment the three dimensionalappearance or surface texture can be accomplished by surface finishingat least a portion of the parallel surfaces of a brake disk substrate toimpart variations in the height of the parallel surfaces to allow thefinished surfaces to receive varying amounts of the particles of acoating material. Methods for applying the coating materials aredescribed below in more detail.

The surface finish can be introduced to the brake disk surface byutilizing a variety of methods. These methods can be as simple asblasting the brake disk surface with a continuous stream of particles(commonly referred to as bead blasting) which are typically harder thanthe brake disk surface. These particles can be round in shape or veryirregular in shape. The various particle shapes will impart a differentsurface finish or surface geography to the brake disk. For example, withthe round particles (of various sizes) and appropriate particle energy(air pressure or hydro pressure) a surface texture that microscopicallyresembles low soft rolling hills can be achieved. With the irregular(crystalline) shaped particles a very coarse surface geometry (veryrugged/jagged peaks and valleys) can be imparted to the brake disksurface. Other methods such as a sanded or a ground surface finish canbe used to give a different appearance when coated with the wear andcorrosion resistant coating. When the sanded or ground surface finish isdone in a cross-hatched configuration and then coated with the wear andcorrosion resistant coating the coated brake disk can exhibit a wovenappearance or surface texture such as is found in components made fromcarbon fiber. In general, there is a multitude of surface finishtechniques that can be utilized to impart a specific surface texture orgeometry into the brake disk. These techniques can include but are notlimited to: bead blasting, sanding, grinding, acid etching, laseretching, photochemical etching, roll forming, embossing, stamping,honing, lapped, polished, blanched, milled, profiled or other additionalmachined surfaces and any combination(s) thereof. In one embodiment atleast a portion of the parallel surfaces of the brake disk substrate issurface finished to impart a predetermined surface finish, irregularity,modification or defect that exhibits a three dimensional appearance orsurface texture. The surface irregularity or defect can be variations inthe height of the parallel. In addition the surface irregularity ormodification can be formed as peaks, valleys and angular surfaces on theparallel surfaces of the brake disk. When the parallel surfaces of thedisk brake is subsequently coated with a coating (as described below),the disk brake exhibits a three dimensional appearance or surfacetexture. The surface texture can be enhanced by controlling thedepositing of the coating, for example, by depositing more of thematerial on the peaks and less of the material on the angular surfaces.This can enhance the resulting surface texture. Additionally, thecoating can be selected such that a desired absorption or reflection oflight is achieved. In addition the composition and thickness of thecoating material to achieve a desired light reflection and absorptionaccording to a specific wavelength. Further, the surface texture caninclude a representation of a logo or artistic design.

Referring now to FIG. 3A, a coating 24 is shown applied to a brake disksubstrate 26. For the brake disk 12, the brake disk substrate 26 can bemade of a cast iron, stainless steel or light weight ceramic compositematerials. As further shown in FIG. 3A, the coating 24 can include afirst layer 28 of a material having an amorphous structure (i.e. anon-crystalline structure) or a crystalline structure. The first layer28 can include multiple layers or multiple surfaces that can be mergedto form a single layer. The thickness of each layer can vary from one ora few atoms in depth to thousands of Angstroms. The surface irregularityor defect can be variations in the height of the parallel surfaces andangled surfaces between the variations in height illustrated in FIG. 3B.In addition the surface irregularity or modification can be formed aspeaks, valleys and angular surfaces between the peaks and valleys. Whenthe parallel surfaces of the disk brake is subsequently coated with acoating the disk brake can exhibit a three dimensional appearance orsurface texture In addition the composition and thickness of the coatingmaterial can be selected to achieve a desired light reflection andabsorption. In some embodiments, the amorphous or crystalline materialis a metal such as titanium, chromium, zirconium, boron, hafnium or analloy thereof

Continuing with FIG. 3A, the coating 24 can also include a second layer30 that overlays and contacts the first layer 28. Though the layers aredepicted as distinct, in some embodiments, the layers intermingle ormerge such that no distinct boundary exists between the layers. Thesecond layer 30 can include one or more binary metals, for example, oneor more metal nitrides, metal borides, metal carbides and metal oxides.The second layer can include one or more nitrides, borides, carbides oroxides of the metal used in the first layer. In some embodiments of acoating 24, amorphous titanium constitutes the first layer 28 and atitanium nitride (TiN, Ti₂N, etc.) constitutes the second layer 30. Themultiple layers, for example layers 28 and 30 can be configured to forma lattice structure or a super lattice structure. These are thin filmsformed by alternately depositing two different components to formlayered structures. Multilayers become superlatices when the period ofthe different layers is less than 100 Å. With this cooperation ofstructure, a coating 24 having a service life to exceed approximately100,000 vehicle miles or more can be obtained. Note: the abbreviations(e.g. TiN, Ti₂N, etc.) are used herein as a shorthand rather than anexact chemical label, and do not suggest that the stoichiometry of theindicated compound must be exactly as stated in the abbreviation.

Referring now with cross-reference to FIGS. 4 and 5 , an exampleapparatus for forming the coatings will be described. A fixture 34 isshown for holding the brake disk substrates 26 during coating. Althoughthe fixture 34 is shown holding five brake disk substrates 26 a-e, it isto be appreciated that the fixture 34 is merely exemplary and that feweror more brake disk substrates 26 could be positioned on a fixture 34. Asshown, the fixture 34 includes three parallel poles 36, 38, 40 that aremounted on and extend from a base plate 42. Although the fixture 34 onlyshows three parallel poles 36, 38, 40 it is appreciated that thisconfiguration is only exemplary and that fewer or more parallel polescould be positioned on the fixture 34. The parallel poles 36, 38, 40 arearranged on the base plate 42 with each pole 36, 38, 40 spaced at anequal distance from the other two poles 36, 38, 40. With thiscooperation of structure, a plurality of brake disk substrates 26 can bestacked on each pole 36, 38, 40. For example, as shown, brake disksubstrates 26 a and 26 d are stacked on pole 36, brake disk substrate 26c is stacked pole 38 and brake disk substrates 26 b and 26 e are stackedon pole 40.

Continuing with cross-reference to FIGS. 4 and 5 , it can be seen thatspacers 44 a-e can be used to selectively separate adjacent brake disksubstrates 26 on each pole 36, 38, 40. For the implementation shown,each spacer 44 a-e includes a tube 46 and flange 48 allowing each spacer44 a-e to be slid over a respective pole 36, 38, 40 and positioned asdesired. In the implementation shown in FIGS. 4 and 5 , the spacingbetween poles 36, 38 is established to allow the brake disk substrates26 on one pole 36, 38, 40 to overlap the brake disk substrates 26 on anadjacent pole 36, 38, 40. Also for the implementation shown in FIGS. 4and 5 , the spacers 44 a-e have been sized to prevent brake disksubstrates 26 on one pole 36, 38, 40 from contacting the brake disksubstrates 26 on an adjacent pole 36, 38, 40.

FIGS. 6 and 7 depict an example of a deposition apparatus 50 for coatingthe brake disk substrates 26, although other operable depositionapparatus may be used. The deposition apparatus 50 includes a chamber 52having a body 54 and a door 56 that may be opened for access to theinterior of the chamber 52 and which is hermetically sealed to the body54 when the chamber 52 is in operation. The interior of the chamber 52is controllably evacuated by a vacuum pump 58 pumping through a gatevalve 60. The vacuum pump 58 includes a mechanical pump and a diffusionpump operating together in the usual manner. The interior of the chamber52 may be controllably backfilled to a partial pressure of a selectedgas from a gas source 62 through a backfill valve 64. The gas source 62typically includes several separately operable gas sources. The gassource 62 usually includes a source 62 a of an inert gas such as argonand a source 62 b of Nitrogen gas, each providing gas selectively andindependently through a respective selector valve 65 a or 65 b. Othertypes of gas can also be provided as desired, such as gases required toproduce borides, oxides and/or carbides.

The pressure within the chamber 52 is monitored by a vacuum gage 66,whose output signal is provided to a pressure controller 68. Thepressure controller 68 controls the settings of the gate valve 60 andthe backfill valve 64 (and, optionally, the selector valves 65),achieving a balance of pumping and backfill gas flow that produces adesired pressure in the chamber 52 and thence pressure reading in thevacuum gauge 66. Thus, the gaseous backfilled atmosphere within thechamber 52 can be a flowing or dynamic atmosphere.

At least two linear deposition sources 70 are mounted within theinterior of the chamber 52 in a circumferentially spaced-apart manner.In FIG. 6 , the four deposition sources are identified as distinctsources 70 a, 70 b, 70 c, and 70 d, as they will be addressedindividually in the subsequent discussion. The four deposition sources70 are generally rectangular bodies having a greatest rectilineardimension elongated parallel to a source axis 72. This type ofdeposition source is distinct from either a stationary point source or apoint source that moves along the length of the substrate 26 duringdeposition procedures.

A support 74 is positioned in the chamber 52. The support 74 produces acompound rotational movement of a fixture 34 mounted thereon. Thesupport 74 can include a rotational carriage 76 that rotates about anaxis 78, driven by a rotational drive motor 80 below the rotationalcarriage 76. Mounted on the rotational carriage 76 are at least one, forexample six as shown, planetary carriages 82. The planetary carriages 82are rotationally driven about a rotational axis 84 by a planetary drivemotor 86 below the planetary carriages 82. The speeds of the rotationaldrive motor 80 and the planetary drive motor 86 are controlled by arotation controller 88. The rotation controller 88 can rotate therotational carriage 76 at a rate of about 1 revolution per minute (rpm).

Continuing with FIGS. 6 and 7 , for deposition processing of brake disksubstrates 26, a fixture 34 as described above can be mounted on theplanetary carriage 82, as shown. For commercial operations, a fixture 34having a plurality of brake disk substrates 26 is typically mounted oneach planetary carriage 82 in the manner described, as illustrated forone of the planetary carriages 82 in FIG. 6 .

The temperature in the chamber 52 during deposition is controlled usinga heater 92 that extends parallel to the deposition sources 70 on oneside of the interior of the chamber 52. The heater 92 can be a radiantheater operating with electrical resistance elements. The temperature ofthe heating array is monitored by a temperature sensor 94 such as aninfrared sensor that views the interior of the chamber 52. Thetemperature measured by the sensor 94 is provided to a temperaturecontrol circuit 96 that provides the power output to the heater 92.Acting in this feedback manner, the temperature controller 96 allows thetemperature of the heating array to be set. In the processing phase, theheating array can be heated to a temperature of from about 1000.degree.F. to about 1700.degree. F.

FIG. 8 illustrates a cathodic arc source 100 that can be used in thedeposition source 70. The cathodic arc source 100 includes achannel-shaped body 102 and a deposition target 104. The depositiontarget 104 is in the form of a plate that is hermetically sealed to thebody 102 using an O-ring 106, forming a water-tight and gas-tight hollowinterior 108. The interior 108 is cooled with cooling water flowingthrough a water inlet 110 and a water outlet 112. Two spirally shaped(only sections of the spirals are seen in FIG. 8 ) permanent magnets 114extend parallel to the source axis 72. Positioned above the depositiontarget 104 exterior to the body 102 is a striker electrode 118. Avoltage V.sub.ARC is applied between the striker electrode 118 and thedeposition target 104 by an arc source power supply 120. V.sub.ARC canrange from about 10 to about 50 volts.

The metallic material that forms the deposition target 104 is depositedonto the brake disk substrate 26 together with, if desired, gas atomsproducing gaseous species from the atmosphere of the chamber 52. For theembodiment describe herein, the deposition target 104 is made ofTitanium (Ti) metal.

To accomplish the deposition, an arc is struck between the strikerelectrode 118 and the deposition target 104, locally heating thedeposition target 104 and causing Titanium atoms and/or ions to beejected from the deposition target 104. (The deposition target 104 istherefore gradually thinned as the deposition proceeds.) The strikingpoint of the arc on the deposition target 104 moves in a racetrackcourse along the length of the deposition target 104. A negative biasvoltage V_(BIAS) is applied between the deposition target 104 and brakedisk substrate 26 by a bias power supply 122, so that any positivelycharged ions are accelerated toward the brake disk substrate 26.

V_(BIAS) can range from about −20 to about −1000 volts. The valueselected for V_(BIAS) determines the energy of ionic impact against thesurface of the substrates, a phenomenon termed ion peening. In a typicalcase, V_(BIAs) is initially selected to be a relatively large negativevoltage to achieve good adherence of the metallic first layer 28 (seeFIG. 3A) to the brake disk substrate 26. V_(BIAS) is subsequentlyreduced (made less negative) when the overlying hard layer is deposited,to achieve a uniform, fine microstructure in the overlying layer. Thevalues of V_(BIAS) are desirably maintained as low as possible,consistent with obtaining an adherent coating 24. V_(BIAS) is morepositive than −600 volts, for example −400 volts and more. If V_(BIAS)is too negative, corona effects and back sputtering may occur at someregions of the brake disk substrate 26. Thus, while higher V_(BIAS)voltages may be used in some instances, generally V_(BIAS) can be morepositive than −600 volts. The cathodic arc source 100 and other types ofsources, such as sputtering sources, may also be used.

The cooperative selection of the material of the deposition target 104and the gases introduced into the deposition chamber 52 from the gassource 62 allows a variety of coatings 24 to be deposited onto the brakedisk substrate 26, within the constraints discussed previously. Thetotal thickness of the coating 24 can range from about 0.5 to about 50.0microns. If the coating thickness is less than about 1 micrometer, thephysical properties of the coating 24 are insufficient to produce thedesired results. If the coating thickness is more than about 10micrometers, the coating 24 has a high internal stress that leads to atendency for the coating 24 to crack and spall away from the brake disksubstrate 26 during deposition or during service.

These general principles are applied in preparing the coatings 24 ofinterest, as described previously in relation to FIG. 3A. The coating 24of FIG. 3A includes an amorphous metallic first layer 28, such asamorphous metallic Titanium, that contacts and overlays the surface ofthe brake disk substrate 26. The amorphous metallic first layer 28 isdeposited by backfilling the deposition chamber 52 with a small partialpressure of about 5 microns of an inert gas, such as flowing argon(flowing at a rate of about 200-450 standard cubic centimeters perminute (sccm) in the apparatus used by the inventors), and thendepositing metal, such as Titanium, from the deposition target 104 withV_(BIAS) about −400 volts. Because the argon does not chemically reactwith the metal, an amorphous metallic first layer 28 is deposited.

As shown in FIG. 3A, a second layer 30, which for the embodimentdescribed herein is a metal Nitride, overlies the amorphous metallicfirst layer 28. The second layer 30 is deposited by backfilling thedeposition chamber 52 with a small partial pressure of about 5 micronsof flowing Nitrogen (flowing at a rate of about 150-500 seen in theinventors' apparatus), and then depositing metal, such as Titanium, fromthe deposition target 104 with V_(BIAS) about −50 v

While the particular brake disks and drums, surface finishes and methodsfor coating as herein shown and disclosed in detail are fully capable ofobtaining the objects and providing the advantages herein before stated,it is to be understood that they are merely illustrative. The describedsystems and methods can also be applied to other systems such as clutchplates, clutches and flywheels. No limitations are intended to thedetails of construction or design herein shown other than as describedin the appended claims.

What is claimed is:
 1. A method for manufacturing a coated brake diskhaving parallel surfaces comprising: surface finishing at least aportion of the parallel surfaces of a brake disk to impart apredetermined three dimensional surface texture having peaks, valleysand angular surfaces between the peaks and valleys; applying a firstmaterial to at least a portion of the parallel surfaces of the brakedisk through vapor deposition, wherein the first material is depositedonto the brake disk by energizing a first material source to causecharged particles of the first material source to be dissociated fromthe first material source and deposited on the parallel surfaces of thebrake disk; and applying at least a compound to the at least a portionof the parallel surfaces of the brake disk through vapor deposition,wherein the second compound is deposited by energizing a second materialsource to cause charged particles of the second material source to bedissociated from the second material source, introducing a reactive gaswhich reacts with the charged particles of the second material formingthe compound that is deposited on the parallel surfaces of the brakedisk; wherein the combination of the surface finishing and thedepositing causes the at least a portion of the parallel surfaces of thebrake disk to exhibit a selected three dimensional surface texture. 2.The method of claim 1, wherein the first material is a metal with anamorphous structure.
 3. The method of claim 1, wherein the firstmaterial is a metal with a crystalline structure.
 4. The method of claim1, wherein second material is a binary metal.
 5. The method of claim 4,wherein the binary metal is selected from the group consisting of ametal nitride, a metal oxide, a metal boride and a metal carbide.
 6. Themethod of claim 1, wherein the three dimensional surface texture isselected from the group consisting of a woven structure and a texturedstructure.
 7. The method of claim 1, wherein surfacing finishing can beachieved by techniques selected from the group consisting of beadblasting, sanding, grinding, acid etching, photo-resist etching, rollforming, embossing, stamping, honing, lapping, polishing, blanching,milling, profiling and combinations thereof.
 8. The method of claim 1,wherein the applying a first material comprises: engaging the parallelsurfaces of the brake disk with a fixture of a deposition apparatuscomprising at least two linear deposition sources with each of thedeposition sources lying parallel to an axis and each of the depositionsources being a source of the first material; and rotating the fixturein a planetary movement about the axis and operating the depositionsources to deposit the first material to the parallel surfaces of thebrake disk.
 9. The method of claim 1, wherein each of the lineardeposition sources is selected from the group consisting of a cathodicarc source, a magnetron sputtering source and an evaporative source. 10.A coated brake disk comprising: a brake disk substrate having parallelsurfaces, at least a portion of the parallel surfaces applied with asurface finish to impart a predetermined three dimensional texture tothe parallel surfaces of the disk brake, wherein the outermost layer ofthe parallel surfaces of the disk brake maintains the predeterminedthree dimensional appearance when coated with at least a first layer ofa first coating material and at least a second layer of a second coatingmaterial by vapor deposition.
 11. The coated brake disk of claim 10,wherein the second coating material is selected from the group ofcoating materials consisting of metal nitride, metal oxide, metal borideand metal carbide.
 12. The coated brake disk of claim 11 wherein themetal nitride is a nitride of an active metal selected from the group ofactive metals consisting of titanium, chromium, zirconium, boron,hafnium and alloys thereof.
 13. The coated brake disk of claim 11wherein the metal oxide is an oxide of an active metal selected from thegroup of active metals consisting of titanium, chromium, zirconium,boron, hafnium and alloys thereof.
 14. The coated brake disk of claim 11wherein the metal boride is a boride of an active metal selected fromthe group of active metals consisting of titanium, chromium, zirconium,boron, hafnium and alloys thereof.
 15. The coated brake disk of claim16, wherein first coating layer comprises a metal with either anamorphous structure and/or a crystalline structure, said metal beingselected from the group of metals consisting of titanium, chromium,zirconium, boron, hafnium and alloys thereof.
 16. A method formanufacturing a coated brake disk having parallel surfaces comprising:surface finishing a portion of the parallel surfaces of a brake disk toimpart a predetermined three dimensional pattern to the portion of theparallel surfaces of the disk brake, the three dimensional patternincluding peaks, valleys and angular surfaces between the peaks andvalleys; applying at least a first layer of coating to the portion ofthe parallel surfaces of the brake disk with at least a first coatingmaterial through vapor deposition; and applying at least a second layerof coating to the portion of the parallel surfaces of the brake diskwith at least a second coating material through vapor deposition whereinmore of the second layer of coating is deposited on the peaks than isdeposited on the angular surfaces between the peaks and valleys; whereinthe outermost layer of the parallel surfaces of the brake disk maintainsthe predetermined three dimensional appearance after depositing the atleast first and at least second layers.
 17. A method for manufacturing acoated brake disk having parallel surfaces comprising: surface finishingat least a portion of the parallel surfaces of a brake disk to impart apredetermined three dimensional surface texture having peaks, valleysand angular surfaces between the peaks and valleys; applying a firstmaterial to at least a portion of the parallel surfaces of the brakedisk through vapor deposition; and applying at least a second materialto the at least a portion of the parallel surfaces of the brake diskthrough vapor deposition, wherein more of the second layer of coating isdeposited on the peaks than is deposited on the angular surfaces betweenthe peaks and valleys; wherein the combination of the surface finishingand the application of the first and second materials causes the atleast a portion of the parallel surfaces of the brake disk to exhibit apredetermined three dimensional surface texture.
 18. The method of claim17, wherein surfacing finishing can be achieved by techniques selectedfrom the group consisting of bead blasting, sanding, grinding, acidetching, photo-resist etching, roll forming, embossing, stamping,honing, lapping, polishing, blanching, milling, profiling andcombinations thereof.
 19. The method of claim 1 wherein the firstmaterial source and the second material source are the same material.